A sheet stacking device is known from Osburg et al., U.S. Pat. No. 4,484,736, which consists of pairs of sheet guide bands with separator and stop plates positioned inbetween, individually raisable and lowerable boundary plates and sheet guide skids which may also be shifted transversely with respect to the sheet flow. This sheet stacking device disclosed by Osburg et al. does not allow for the dense occupation of the stack surface with sheet guide bands as desired in some applications. Typically, inflowing sheets are blown against the bands by means of an air stream from underneath such that there is a tendency, particularly in the case of relatively thin sheets, that the sheets will arch upward between the bands and no longer rest in faultless alignment with the rest of the previously stacked sheets. Osburg et al. also discloses vertical movement of the boundary plates and guide skids otherwise joined firmly with the bearing of the band pair concerned, and serves merely to remove individual ones of these plates or skids so as not to interfere with the sheets passing through.
It is an object of the present invention to provide a sheet stacking device which may easily accommodate a variety of sheet formats such that the inflowing sheets may be well supported by a large number of sheet guide bands.
It is another object of the present invention to provide a sheet stacking device such that format adjustment will be done automatically by control of a microprocessor.
The above objects are realized in the present invention by providing a sheet stacking device with a relatively dense arrangement of guide bands, for example separated by a gap of only 75 mm., which may be shifted individually in a lateral direction through a limited interval. This limited lateral movement of the guide bands is enough to allow for the insertion of boundary plates and guide skids between the guide bands such that they may be positioned anywhere along the total width of the stacking area.